Tested: SRAM XX1 Eagle Drivetrain

SRAM’s 1x12 mountain bike drivetrain may upset one of the final reasons to be a 1x holdout

Despite the popularity of SRAM’s 1x11 drivetrains, some riders have remained holdouts, citing the system’s limited range of gears. But with its 12-speed Eagle groups, the company might finally have killed the front derailleur. By squeezing 12 cogs into the same space as 11, engineers created a 500 percent range (your hardest gear is five times the ratio of your easiest) that’s close to that of some 2x setups, and much wider than the 420 percent gear range of an 11-speed, 10-42 cassette.

The group is available in SRAM’s top-of-the-line XX1 version, which is intended for XC racing and trail use, while X01 Eagle covers trail to enduro riders—it’s $224 less than XX1, but weighs 46 grams more and has a more bombproof construction.

SRAM’s current XD driver can still be used, but everything else is new. Since the Eagle cassette uses the same 10-42 gear range and spread for its first 11 cogs, it felt familiar until I got to the 12th, 50-tooth cog. The jump from 42 to 50 is slightly larger than the other shifts on the cassette, causing a bigger change in cadence, but the actual shift is smoother than the previous jump from 36 to 42 cogs on the 11-speed groups, thanks to new shift ramp profiles in Eagle that more smoothly guide the chain onto the 50-tooth cog. XX1 features the gold-colored titanium nitride finish, while X01 comes in traditional silver.

Having a 50 in the back isn’t just about having a very low climbing gear; it enables you to gain back the high end of the range in a 1x setup by using a larger chainring (like a 36- or 38-tooth). But some frames may not have the clearance to run a chainring that big. Setup and tuning is more fickle too, as tolerances tighten up with the 12-speed system. (Learn how to handle these and other issues in The Bicycling Guide to Complete Bicycle Maintenance and Repair.) Cable tension and B-tension clearance (the distance between the upper pulley wheel and the cogs) seem to be even more critical than before. And there is a 34-gram weight penalty compared with the 11-speed XX1.

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